After shifting its customer focus over the past year a bit, battery startup Leyden Energy announced on Wednesday that it’s closed a series C round of $10 million to continue to work on commercialization. The company was previously looking to sell its next-generation lithium ion batteries for e-bikes, electric vehicles, laptops and even the power grid, but is now more focused on tablets and start stop vehicle tech.

Leyden Energy was founded in 2007 (formerly called Mobius Power) with a patent acquired from chemical giant Dupont, and a $4.5 million investment from investors. Leyden’s original secret sauce is an innovation for the electrolyte part of the battery. A battery has a positive and a negative plate and then an electrolyte in between, which is the substance through which electrons transfer back and forth while the battery charges and discharges.

In addition to its electrolyte innovation, Leyden also has a new breakthrough technology for a silicon anode that boosts the energy density (amount of energy stored per volume) and enables the battery to be made in a very slim form factor. Many battery companies combine next-generation technology in each part of the battery to produce a better whole battery in production.

Making lithium ion batteries slim is a priority for Leyden. It’s recently been focused on tablets and consumer electronics and announced an effort with chipmaker NVIDIA to design tablets; it also has been courting makers of chargers for smart phones and devices for personal Wi-Fi hot spots. A couple years ago Leyden launched a replacement lithium-ion battery for laptops that won’t degrade (start losing its full charge) for at least three years, and will come with a three-year warranty.

Start-stop vehicle tech, which uses a battery to automatically cut off the engine of a gas-powered vehicle while it’s idling, is another target area for Leyden. Start-stop vehicle technology is starting to gain momentum in Europe, following carbon reduction regulations, and the technology can reduce fuel use by 5 to 12 percent.

These are difficult times for battery startups right now, particularly those that were hoping the electric car market would take off faster than it has. Lithium ion battery leader A123 Systems recently went bankrupt and then was sold to Chinese auto parts giant Wanxiang. Battery maker Ener1 also filed for bankruptcy last year.

But there’s still some rare next-gen battery startups looking to innovate around new materials, new production techniques, and nanotechnology. Here’s 13 battery startups to watch in 2013.

Leyden’s series C round of $10 million came from existing investors including NEA, Lightspeed Ventures, Sigma Partners and Walden International. The company has raised $48 million in venture capital since it was founded.